The present invention relates generally to cutting bits (tools), which can be applied for excavation, planing, drilling and surface finish of the sock, concrete, soil and other non-metallic materials and be mounted on corresponding equipment, intended for cutting (treatment) of the above mentioned materials.
Cutting bits of the above mentioned general type are known in the art.
The typical disadvantages of the existing cutting bits are their limited strength and the cutting edge and blade of the cutting bits after certain period is subjected to dulling and breaking.
It is therefore believed to be clear that it is desirable to improve the existing cutting bits in these aspects.
A plurality of tool have been developed with the objective to protect cutting bits from breakage and intensive fast wear.
U.S. Pat. No. 1,174,433 discloses flat one-bladed cutter set with cutting element having convex front face and sole cutting edge, of the limited length. Said bit has sufficient cutting ability but insufficient durability and reliability.
U.S. Pat. Nos. 4,538,691 and 4,678,237 disclose flat one-bladed tools set with cutting element having flat face, oriented at a substantial negative rake angle, that can protect bit cutting edge from overloading by providing a lifting force, but reduce bit cutting ability and wear resistance.
U.S. Pat. Nos. 4,538,690; 4,558,753 and 4,593,777 discloses flat one-bladed bit set with cutting element having concave front face, oriented at a large negative rake angle that can prevent bit overloading for uniform rock destruction; however, described tools have insufficient cutting ability and wear resistance.
U.S. Pat. No. 5,078,214 discloses round one-bladed bit set with cutting element having flat or concave front face, that decreases bit strength due to shear stresses generation within cutting element.
U.S. Pat. No. 5,496,131 discloses round one-bladed bit of the road planing cutter, set with replaceable cylindrical cutting element, having flat or concave front face that can increase bit cutting ability but decreases its durability and reliability.
U.S. Pat. No. 5,520,444 discloses round one-bladed bit set with cylindrical cutting element having convex front face but devoid of side cutting edge that can decrease bit cutting ability, especially in corner zones.
German Patent Nos 3234521 and 3336154 discloses one-bladed round tubular chisel, set with cutting element, having concave front face and limited included angle; bit front face is oriented at significant positive rake angle. Combination of the bit listed signs provided bit insufficient strength and wear resistance.
USSR Pat. No. SU-1671850-A1 discloses round one-bladed cutter set with cylindrical cutting element having flat front face, oriented at a substantial negative rake angle that can increase bit strength but decrease its cutting ability and wear resistance.
Accordingly, it is an object of the present invention to provide a cutting bit, which is a further improvement of the existing cutting bits of this type. In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a cutting bit, which has a bit body, and a cutting element formed as a trihedron with three curvilinear convexo-convex outer faces, which form the material destructing blades, so that the cutting bit can be turned to orient alternatively a respective one of the destructing blades in a cutting direction in the event of dulling or breaking of the destructing blades.
When the cutting bit is designed in accordance with the present invention, then after dulling or breaking of one of the faces of the cutting element which forms the corresponding cutting blade, the bit body together with the cutting element is turned so that another face or in other words a new material destructing blade is oriented in the cutting direction and that not worn and not damaged face or cutting blade can now successfully cut material and the like.
As a result, the service lifetime of the bit is increased since effective length of the cutting edge is trebled; the bit has high strength because bit cutting faces are convexo-convex and therefore promote generation within these faces materials (especially, carbide and other hard brittle alloy) predominant compressive stresses, instead of destructive shear and tensile ones; and the bit has high destructive ability due to the presences of lateral cutting edges.
In accordance with another embodiment of the present invention, the cutting element in a cross-section is formed as a triangle, which can have sides of the different lengths and inner (included) angles of the different values. In this case, the bit can be applied for destructing of the materials which are substantially distant from one another with regard to their hardness and other properties. That is, a fixed setting of a plurality of bits can be optimized for penetration ability or surface finish solely by choice of proper bit face orientation.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.